1. Field of the Invention
This invention relates to methods and devices for bacterial, fungal and/or viral sterilization and disinfection, and is more particularly directed to a UV-C disinfection apparatus and system for ultraviolet and near-ultraviolet germicidal irradiation.
2. Description of Related Art
Ultraviolet germicidal irradiation (UVGI) is a disinfection method that uses short-wavelength ultraviolet (UV-C) light to kill or inactivate microorganisms. One mechanism by which UV-C deactivates microorganisms is by destroying nucleic acids and disrupting their DNA, leaving them unable to perform vital cellular functions. The administration of UV-C radiation is becoming widely adopted by many hospitals as a more effective and reliable means of surface disinfection, as compared to the use of chemical cleaning agents alone. The effectiveness of germicidal UV-C irradiation depends on factors such as the length of time a microorganism is exposed to UV-C, the intensity and wavelength of the UV-C radiation, the presence of particles that can protect the microorganisms from UV, and a microorganism's ability to withstand UV-C during its exposure. In air and surface disinfection applications, the UV effectiveness is estimated by calculating the UV dose to be delivered to the microbial population. A method of calculating UV dose is as follows: UV dose μWs/cm2=UV intensity μW/cm2×Exposure time (seconds).
Germicidal UV for disinfection is most typically generated by a mercury-vapor lamp. Low-pressure mercury vapor has a strong emission line at 254 nm, which is within the range of wavelengths that demonstrate strong disinfection effect. The optimal wavelengths for disinfection are close to 265 nm. UV-C LEDs use semiconductors to emit light between 255 nm-280 nm. The wavelength emission is tunable by adjusting the material of the semiconductor. The use of LEDs that emit a wavelength more precisely tuned to the maximal germicidal wavelength results in greater microbe deactivation per amp of power, maximization of microbial deactivation for the available, less ozone production, and less materials degradation. Embodiments of the present disclosure provide for a disinfection fixture that reduces exposure time by varying the intensity and wavelength of the UV-C administered. Like UVGI, near-UV (violet-blue) light, particularly 405 nm light, has significant antimicrobial properties against a wide range of bacterial and fungal pathogens. Unlike UVGI, near-UV is safe for continuous use in occupied environments. Consequently, a hybrid arrangement allows for the optimum deployment of both UVGI and near-UV in a closed-loop disinfection process and also provides general area illumination.